Posted
by
samzenpuson Monday July 23, 2012 @11:46AM
from the look-at-the-energy dept.

Elliot Chang writes "A team from UCLA has developed a new transparent solar cell that has the ability to generate electricity while still allowing people to see outside. In short, they've created a solar power-generating window! Described as 'a new kind of polymer solar cell (PSC)' that produces energy by absorbing mainly infrared light instead of traditional visible light, the photoactive plastic cell is nearly 70% transparent to the human eye — so you can look through it like a traditional window."

Transparency is merely how much of the light gets through. What you are talking about is translucency (i.e. scattering). There's no indication from the article that there is significant scattering. It would just look like you had tinting on the window.

Transparency is merely how much of the light gets through. What you are talking about is translucency (i.e. scattering). There's no indication from the article that there is significant scattering. It would just look like you had tinting on the window.

And not very much tinting, either. 70% transparent would just look like glass, if you didn't have something to compare it to. Even 90% tinting (10% transparent), as long as it is reasonably uniform at different color transmissions, doesn't interfere with vision at all... sunglasses block more light than that!

I think his point was that if you were inside a building that all the windows had the exact same 70% transparency, you'd have a hard time answering the question "is there tinting on this window". Whereas if someone said "here's two windows" and one was 70% and one was 90%, you'd be able to totally tell the difference. We're just not that good at detecting the difference between "full daylight" and "70% of full daylight", unless we're directly comparing the two.

I was just thinking this sounds like a nice way to get some power from your tinting. But I wonder how useful it is in reality? And attaching wires to a roll-down window will increase mechanical complexity and add will eventually wear out the wires leading to the window or whatever track mechanism you're going to use to transfer power.

I assume this has been tested to work with safety glass? And you can't tint your front or rear windows legally. Probably would make getting a window replaced significantly

Simulated windows only work when you are stationary. once you move the illusion dissipates and you only perceive them for what they really are (failed mind controlling devices designed with the disillusioned hopes of making you work harder) from then on.

Would be more effective to get rid of the windows entirely (or shrink them to tiny size), since there is more energy LOSS through the window than any other part of the house. Thousands of kilowatt-hours of heat (or cool) leak through glass via conduction. Meanwhile the embedded-solar would only generate a few hundred. Overall a huge net loss.

From the units posted on the graph, the windows in the Passivhaus are emitting radiation consistent with a 1-2C increase in temperature (or, rather, the difference between 37/39.2F and 41F), while those for the traditional structure are consistent with a ~4C increase in temperature (or, rather, the difference between 37/39.2F and 46F). (Compared to double-pane, low-E, R-3 (U-factor 0.3) windows, triple-pane windows (typically R-5/U-factor 0.2) can reduce average heat loss through the window by more than 30

Given that untinted window glass is in the 80-90% range, 70% isn't bad at all.

Remember that you don't perceive brightness linearly. Its several orders of magnitude brighter outside on a sunny day than it is in a very well-lit room inside, but it doesn't feel that way. Think of how many light bulbs you'd need to have to match 1000W/m^2, factoring in also that even fluorescent and LED bulbs lose the lion's share of their energy as heat.

Windows have what's known as a VT rating or visible transmittance rating. Just a plain pane of glass 3-4 mm thick has a VT of about 90-93%. Two such panes bring it down to 80-86%, and that's without any other kind of coating or anything else. Some windows on the market today have a VT of just 15%, and people still buy them . To most people at VT of about 60% looks clear. 30% on this technology would give a 70% VT if nothing else reduces it.

Want to sound like a fourth grader shilling their science project? Use exclamation marks in your summary.

I'm not sure if the summary has been changed since you posted, but here is what I currently see:

A team from UCLA has developed a new transparent solar cell that has the ability to generate electricity while still allowing people to see outside. In short, they've created a solar power-generating window! Described as 'a new kind of polymer solar cell (PSC)' that produces energy by absorbing mainly infrare

The company XSUNX has been doing this for a few years with Copper Indium Gallium Diselenide (as a competitor to Silicon and which theoretically is supposed to be better for the environment), generating thin film solar power that you can see through. Their first generation was a smoky amber glass with slight distortion; their current generation film is more like a tinted window.

Unclear how much energy you get in exchange for adsorbing 30% of the visible light and probably all the IR. However, if its a lot of light, it might be worthwhile to dip old fashioned incandescent bulbs into this goo. Rather optimistically, if it can generate more than 40% of the nameplate wattage by adsorbing all the IR and 30% of the visible, then you'd get ahead by recycling that power back into the grid. Not a perpetual motion machine, because 70% of the visible is still leaking out the lampshade, but it would be like the world's weirdest phosphor basically eating IR photons and emitting visible photons.

This does bring up the interesting point for unshaded windows, if it eats 30% of visible light, that merely means you need 30% more ultra-low-R value window area, or 30% more lightbulbs inside to brighten the room back up. So its not going to work well for windows in rooms where the drapes are always open and people are always inside. Great idea for my garage or bedroom (why do those have windows, anyway?) terrible idea for my office / kitchen / living room. Solar panel covered shutters seem like a good idea for the garage and bedroom... if the panels are rockin don't come a knockin or whatever.

It can't be more efficient than using light sources that don't emit the IR radiation in the first place.

If a room is well-lit by windows, you don't need any additional window to remain well-lit. A 30% reduction in light for something that's well-lit, particularly by daylight, is not really noticeable. (Rather, you can only tell if you have both available for comparison. If you reduced the transmission of your windows by 30%, your eyes would simply adjust.)

We'll just make a heat reservoir and hook it up to a heat pump that pumps in heat from outside with a COP [wikipedia.org] of well-greater-than-1, and we'll surround the reservoir in highly efficient IR-absorbing panels, which will capture almost all of the energy, driving the heat pump and yielding energy to spare. Perpetual motion! Take that, laws of physics!

Whether you're dealing with a physical "engine" or not, Carnot must be obeyed, because if he's not, a high-COP heat pump can pump in more heat against the gradient

If efficiency is comparable to other cells, a good efficiency would be around 25%. Also, IR light is lower in the energy EM spectrum. I don't know how important it could in that case, we do not have much information about these new panels.

In cold climates, these panels may not be a good idea since instead of reflecting IR, it absorbs it. So, a part of the energy spent to heat the building will feed these panels instead of heating the inside. Again, we need more data to compare both alternatives.

Well, as mentioned elsewhere, you're limited not just by the standard issues of solar cells, but also by more relevant entropy limits. If your solar cell is being hit by ambient radiated heat IR and is radiating IR in the same range, it's impossible to generate power without violating the laws of thermodynamics. Even though it's not technically a heat engine, you can treat a solar cell as an indirect heat engine subject to the limits of Carnot's theorum (as Carnot's theorum is simply a direct consequence

Absorb and adsorb are two different things, they are not interchangable (however they are similar). If something absorbs water, it means it draws water into it, while if it adsorbs water, it means it holds the water to its surface. Either phenomena would result in the material picking up the water, so the end result is more or less the same. Unless you're sure you mean adsorb, just use absorb to refer to one object taking in another.

That said, if adsorb really is the technically appropriate term here, I

if you could work out the whole 'light uses AC, generator makes DC' issue while maintaining the cost advantage.

Incandescents work perfectly on DC. You other argument was important though.

Nice thought, but I just don't see that working. I like incandescent too because they are instant on, (I have yet to find a fluorescent that actually works like this)

fluorescents are slow, true. Try Leds for the instant-on places (like the bathroom, it's hard to aim in the dark), if your house wiring is good enough. Do you really need instant on in the living room? That blinding brightnes at the moment you flip the switch? I'd hate it. I love my slow dimmable fluorescents for those applications.

works in all temperatures (from -40 in winter for outside lights, fluorescent come on VERY slow in winter)

There are low temp fluorescents. They still contain a significant amount of mercury (normal fluores

If this stuff could be further developed so that you would be able to turn it on and off like smart glass it would be a good alternative of shades, generating electricity from excess light. Trying to only convert IR light is a clever idea, but the electricity you get from that isn't much, you are much better off putting a panel on the roof.

So if I replaced a section of optical fiber with this stuff, it would look on the OTDR like the worlds most uninteresting little bump (oh look, sloppy winding in the splice case results in a minor bump, eh who cares) and I could detect the electrical field... Sounds like a optical tap design.

Of course a beam splitter would probably be a lot simpler, but supposedly there does not exist a beamsplitter design that doesn't inherently create what amounts to multipath that "looks like a beamsplitter" on a OTDR so simply doing something weird when you're tapping might help avoid detection.

The only undetectable optical tap I can think of is chilled-PMT based... I think that would be fairly undetectable if done right.

I haven't directly hands on done fiber since early 90s so I'm not sure. Probably fiber work is much like IT and CS, there is nothing new, just recycled old ideas along a baseline of slowly increasing speeds.

The key issue with solar has always been price. It seems forever on the cusp of having a positive ROI, but it never actually breaks through. Hopefully the use of plastic as opposed to crystals will bring the cost way down.

Depending on the efficiency, it might be an interesting choice for something like one (North or South) side of a large glass building, effectively giving you a large solar array for windows that you were going to put in anyway.

If the windows are a lot more expensive don't expect much conversion (pardon pun).

Also the ease of use. If hooking up 4% worth of power to your home and/or the grid is expensive, also do not expect much conversion. (batteries, inverters, wiring, smart meter, etc... is it really worth doing all that for a handful of watts?)

Glass already blocks out most of the IR. The plants don't seem to have any trouble with that. In fact that is one of the ways a greenhouse works. Light enters through the glass, hits the ground (covered with black plastic or dark earth) is converted to IR and radiates out from there. Some of it will hit the plants, some of it will miss and hit the glass. The glass reflects most of it back again. Some of that reflected IR will hit the plants, some will hit the plastic/earth and warm it, and so on.

Actually, from what I understand, greenhouses work because glass is transparent to short-wavelength IR (close to the visible spectrum), but reflects long-wavelength IR (close to microwave). When the short wave IR hits the plants and ground, it gets absorbed and emitted as longer wavelength, which is then trapped inside by the glass.

That's why you can control temp by covering the ground with a white reflective surface; the absorption and re-emission doesn't happen - the short wavelength IR is simply reflec

I seem to recall IR it is blocking is also a major part of heat transference. There could be some definite savings on cooling bills throughout the sun belt/southwest.

Anybody else reminded of the Heinlein stories where Solar panels took off when they started generating energy from the full range of cosmic radiation bombarding the Earth? Led to commuter roads in "The Roads must roll".

I'm a supporter of efforts like the development of these windows. The biggest difference in this world between the haves and the have nots is access to affordable energy. If you get that, you get clean water, refrigeration, air conditioning, transportation, etc.

This is why I am in favor of technology developments that focus on energy generation. I'm against using state power to artificially drive conservation because most of the time that really means making access to energy more expensive. The end r

Don't worry, Some politicians will request a new stimulus package because throwing money in the air has worked so well so far. We will end up funding those Chinese with money we borrowed from them in the process _again_.

I more referring to the fact that should these actually be manufactured using fossil fuels that it would kind of obviate them as a replacement for them since the simple construction of them would be counterproductive to the whole "not using fossil fuels" line of solar power. Thanks for ruining it Professor Killjoke.

There was actually a recent episode of the Straight Dope podcast (which is just reading the weekly column) that covered this. It was a followup to a recent episode that doesn't seem to be available in the feed anymore..

It's really not that complicated. If it's cheap enough, and produces enough power, it will be useful for some people, but will probably not replace Grid Power (though it may help reduce consumption of Grid power, which is generally a win). For other people, because of their circumstances, it will not be so useful.

Therein lies the great, simple truth that most advocates on both sides of the argument ignore.

Solar power (and wind power) isn't a 100% solution for our national energy needs. That doesn't mean it

"Our new PSCs are made from plastic-like materials and are lightweight and flexible," he said. "More importantly, they can be produced in high volume at low cost."

Of course, I'll believe that when I see the bill. However, if it works as they say about the only downside is that you won't get as much heat during cold winters through the windows. That's actually about it. Oh yeah, and they are polymers so they may require oil to be produced (maybe, not sure and don't care enough to find out). Maybe some Slashdoter could get worked up about that or something.

There's solar equipment to power houses that will provide a return on the investment on current power prices in 5-10 years, like expensive 10k+ units.These are from profit companies, if they were not profitable, they would not be in business.Based on economics, this implies that solar cells do actually generate more power than they consume over the lifetime of the cell.

Not all cells or technologies right now naturally, but your generalization cannot be applied to all forms of solar technology.

Depends on the return on investment. Even if the return is positive, there may be more efficient ways to deploy that capital. At least until the technology matures enough to become competitive with alternatives. Of course, the glut of natural gas is pushing that point into the future right now.

In fact, the data that I've seen shows that one type of solar cell (CIGS) can actually *increase* in power output over time. Unlike with silicon cells, where there's a small (usually tapering off) loss over time, the "damage" from ionizing radiation can help remove defects in CIGS cells, functioning as a slow annealing stage.

This is much more interesting for commercial building use than for the home. At home, you're better off shading your windows and just using less AC. Once you get above tree height the math goes the other way. Cover as much of the facade as possible, including vision glass, with photovoltaics. They're already using both transparent and non-transparent photovoltaic on tall building facades.

I think you're overselling how often windows in a house get broken. I haven't had a window break in any house I've lived in for at least 10, if not 20 years. Not to mention, these are plastic, so they are probably harder to break than glass.

Even if solar is far away or never will become a primary energy source it makes a great backup or supplementary source of power. I live in a house that is covered almost entirely with shade except for a portion of my garage. That small portion of garage is another to charge up a dozen of my DC gadgets.

It's not a lot, but it is something. Think of the exposure to sunlight that cars have on the road. Yes... if you can get enough juice out the material it could top off you battery nicely.

Efficiency is not an issue is it. No matter what they do, no solar tech will ever get better than 20% efficient

Fascinating, because just from a quick Google search I find a company selling~30% efficient solar cells [spectrolab.com] today, and that Sharp is at 43.5% [cleantechnica.com] in lab cells. I swear I've seen cells in the 30%s being sold commercially (albeit at very high prices), but I forget which company it was.

The question I would have is if it can produce enough electricity to power an LCD film put over the same window. Slap a battery into the window casing, and you have self powered windows that don't need curtains.

it's all relative. The problem with traditional solar panels is there's a limited area you can place them - typically on the roof, and often at an angle to get the most sunlight, thus reducing the number of panels further.

But if you look at most office blocks, they're practically all glass. Even at 1/5th efficiency of traditional panels, if you can put at least 5 times as much area of them in, then you will get more power out. Ratio of window to roof on a modern skyscraper towerblock is a lot more than 5:1.

That was actually butt-obvious from the context already (especially to anyone who has spent more than three seconds ever checking out solar panel pricing). IMHO you didn't really need to clarify that, just to satisfy some pedantic egotist trying to demonstrate their superiority by pretending your use of units was confusing to anyone 'clued up'.

Solar is already available and affordable for many uses. I expect a calculator (If I ever own a dedicated unit again) to run off of solar power. Solar yard lighting is also heavily used because it is widely available and affordable. Solar for road signs in remote areas, and emergency call boxes are also the norm.

30 years ago, photovoltaic panels were an oddity. Your average person never saw them. Today, they are everywhere. You can't walk through a Walmart without seeing them all over the place for

Why is it that every time a story is posted about a new solar technology, someone replies to say, "We keep hearing about new solar technologies, but they won't make it onto the market for years." Wrong! All these new solar technologies you keep hearing about are making it onto the market. That's one of the reasons solar prices have been dropping like a rock in recent years.

1 skylight. Now get the efficiency of a roof top solar panel... with electricity.

2. Blocking IR is huge for windows. We have a few south facing windows with no shade... just blocking IR through them would be huge (I have thoiught of it before too). Especially in the summer, every unit of energy that I don't have to extract and remove with the AC units is money saved.

Anything on top of that, even a little extra electricity (maybe enough to operate the blinds?) is gravy.

Especially if you'd be tinting the windows anyway. If you can make this stuff for not much more than regular window tinting, then it might end up way ahead of photovoltaics on the roof.

The questions would be (i) how much more expensive than regular tinting, (ii) how much more/less heat ends up in the building versus tinting (this stuff may be more efficient or less efficient at keeping summer heat out of the building than straight tinting) and (ii) what's the cost of the additional wiring you'd need (as yo